Employee Benefits and Stock-based Compensation (Tables)

12 Months Ended

Jan. 31, 2022

Classification of Stock-based Compensation

The following table presents the classification of stock-based compensation for the periods indicated:

	Year Ended January 31,
	2022		2021		2020
	(in thousands)
Stock-based compensation:
Cost of revenue	$	1,489	$	1,328	$	1,184
Research and development		54,787		42,903		41,842
Selling, general and administrative		31,525		25,903		23,845
Total stock-based compensation	$	87,801	$	70,134	$	66,871

Weighted-Average Assumptions Used to Estimate Fair Value

The following table sets forth the weighted-average assumptions used to estimate the fair value of stock options and employee stock purchase plan awards for the periods indicated:

	Year Ended January 31,
	2022			2021			2020
Stock Options:
Volatility		51	%		52	%		52	%
Risk-free interest rate		1.04	%		0.52	%		1.82	%
Expected term (years)		5.06			5.78			6.01
Dividend yield		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		57	%		59	%		47	%
Risk-free interest rate		0.06	%		0.21	%		2.23	%
Expected term (years)		0.5			0.5			0.5
Dividend yield		0	%		0	%		0	%

Stock Option Activities

The following table summarizes stock option activities for the periods indicated:

	Option Outstanding
												Weighted-
										Total Intrinsic		Average
						Weighted-		Weighted-		Value of		Remaining		Aggregate
				Weighted-		Average		Average		options		Contractual		Intrinsic
				Average		Grant-date		Acquisition-date		Exercised		Term		Value
	Shares			Exercise Price		Fair Value		Fair Value		(in thousands)		(in years)		(in thousands)
Outstanding at January 31, 2019		1,459,064		$	28.31
Granted		66,850			50.56	$	25.35
Exercised		(366,886	)		15.52					$	13,263
Forfeited		(14,931	)		46.29
Expired		(19,451	)		64.53
Outstanding at January 31, 2020		1,124,646			32.93
Granted		51,200			59.54	$	28.37
Exercised		(421,736	)		24.52					$	19,401
Forfeited		(11,618	)		46.69
Expired		(23,349	)		70.11
Outstanding at January 31, 2021		719,143			38.33
Granted		14,700			110.19	$	50.28
Assumed		163,581			23.10			$	173.04
Exercised		(269,287	)		28.23					$	25,622
Forfeited		(7,669	)		68.95
Expired		(1,146	)		9.86
Outstanding at January 31, 2022		619,322		$	40.08							5.25		$	61,975
Exercisable at January 31, 2022		399,764		$	42.40								3.92	$	39,076

Restricted Stock and Restricted Stock Units Activities

The following table summarizes restricted stock and restricted stock units activities for the periods indicated:

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2019		2,395,516		$	48.49
Granted		1,329,288			54.54
Vested		(1,012,581	)		51.24
Forfeited		(94,957	)		54.26
Unvested at January 31, 2020		2,617,266			50.30
Granted		1,499,203			53.45
Vested		(1,162,883	)		50.53
Forfeited		(81,785	)		54.48
Unvested at January 31, 2021		2,871,801			51.73
Granted		1,213,257			128.80
Vested		(1,367,309	)		53.85
Forfeited		(66,614	)		71.59
Unvested at January 31, 2022		2,651,135		$	85.41